The discovery of fossil animal bones bearing butchery marks pushes back the known history of tools by almost a million years.

The creatures who wielded the implements pre-date the evolution of the Homo primate family to which modern humans belong.

Previously, it was believed intelligent tool use only started with the emergence of the Homo genus.

Now it is known that a much more primitive ancestor, Australopithecus - which resembled an upright walking ape - understood how to use blade-like stones to strip meat off bones.

Whether it manufactured the tools or used conveniently ready-made stones with sharp edges is not yet known.

Dr Zeresenay Alemseged, from the California Academy of Sciences in the US, who led the researchers responsible for the find, said: "This discovery dramatically shifts the known timeframe of a game-changing behaviour for our ancestors.

"Tool use fundamentally altered the way our early ancestors interacted with nature, allowing them to eat new types of food and exploit new territories. It also led to tool making - a critical step in our evolutionary path that eventually enabled such advanced technologies as aeroplanes, MRI (body scanning) machines, and iPhones."

"This find will definitely force us to revise our text books on human evolution, since it pushes the evidence for tool use and meat eating in our family back by nearly a million years.